Fragments of embryos will be treated with plant lectins conjugated with markers visible in the electron microscope in an attempt to find changes in surface chemical composition which can explain changes in cell behavior. Galactose incorporation into glycoproteins will be studied in normal and hybrid embryos of various developmental stages. Experiments will be performed which will show the intracellular site(s) of galactosylation and the cellular location of galactose-containing glycoproteins. More information about the qualitative nature of glycoproteins synthesized during early development will be obtained with gel electrophoresis. These experiments will be performed with the embryos of Rana pipiens and various interspecific hybrid embryos of the genus Rana. Xenopus laevis and Xenopus mulleri and their hybrids may also be used.